Field of the Invention
This invention is directed to an improved electric heating pad which prevents burns resulting from improper use. More specifically, this invention is directed to an improved electric heating pad which monitors temperatures of surfaces of the heating pad and/or monitors a duty cycle of an internal thermostat to detect when the heating pad is covered.
Discussion of Related Art
Electric heating pads are used by many for pain relief and to improve local blood circulation. However, use of electric heating pads is also associated with severe dangers including shock/electrocution, fire, and skin burns.
Underwriters Laboratories Inc. (UL) has developed and promulgated design rules that effectively mitigated the dangers of shock/electrocution and fire. However, UL has not undertaken a technical program that addresses the skin burn problem. Nevertheless, many heating pad manufacturers have falsely represented that their compliance with UL standards has ameliorated the skin burn propensity of their pads.
For the most part, heating pad manufacturers have attempted minimize the danger of skin burn injuries with the use of on-product and in-manual warnings that have been promulgated by UL, the Food and Drug Administration (FDA), and Consumer Product Safety Commission (CPSC). For example Table 1 shows a typical on-product warning label for an electric heating pad.
TABLE 1DANGERTO REDUCE THE RISK OF BURNS, ELECTRICSHOCK, AND FIRE, THIS PRODUCT MUST BEUSED IN ACCORDANCE WITH THE FOLLOW-ING INSTRUCTIONS: •BURNS CAN OCCURREGARDLESS OF CONTROL SETTING,CHECK SKIN UNDER PAD FREQUENTLY. •DONOT SIT ON, LEAN AGAINST, OR CRUSH PAD-AVOID SHARP FOLDS, ALWAYS PLACE PADON TOP OF AND NOT UNDER YOUR BODY.NEVER PLACE PAD BETWEEN YOURSELFAND CHAIR, SOFA, BED, OR PILLOW. •DONOT USE WHILE SLEEPING. •DO NOT USE ONAN INFANT. •THIS PAD IS NOT TO BE USEDON OR BY AN INVALID, SLEEPING ORUNCONSCIOUS PERSON, OR A PERSONWITH POOR BLOOD CIRCULATION OR DIA-BETES UNLESS CAREFULLY ATTENDED. •DONOT USE ON AREAS OF INSENSITIVE SKIN. •NEVER USE PAD WITHOUT THE CLOTHCOVER IN PLACE. DO NOT USE PINS OROTHER METALLIC MEANS TO FASTEN THISPAD IN PLACE. •DO NOT USE IN OXYGENATMOSPHERE. •NEVER PULL THIS PAD BYTHE POWER SUPPLY CORD. DO NOT USETHE POWER SUPPLY CORD AS A HANDLE.UNPLUG WHEN NOT IN USE. •DO NOT USEPAD WITH LINIMENT, SALVE, OR OINTMENTPREPARATIONS THAT CONTAIN HEAT-PRODUCING INGREDIENTS. SKIN BURNSCOULD RESULT. •CAREFULLY EXAMINEINNER COVER BEFORE EACH USE. DISCARDTHE PAD IF INNER COVER SHOWS ANY SIGNOF DETERIORATION. •READ AND FOLLOWALL INSTRUCTIONS ON BOX OR PACKEDWITH PAD BEFORE USING.However, use of warnings has failed to reduce the burn rate. In fact, the CPSC estimates that the annual number of skin burns due to electric heating pads has increased by 33.9% from 1600 in 1995 to 2142 in 2008. Furthermore, as the number of required admonitions increases, the effectiveness of the warnings decreases as users become overwhelmed reducing the warnings to an exercise in liability proofing.
Most skin burn accidents can be attributed to three reasonably foreseeable misuses of the pads:
1. Covering both faces of the pad—increasing contact temperature or heat transfer to the body.
2. Falling asleep during use—increasing exposure time.
3. Omitting the cloth cover—increasing both the contact temperature and the rate of heat energy transfer to the body.
Some manufacturers have eliminated the third improper use by eliminating removable covers and only including permanent covers with their heating pads. However, this approach fails to eliminate or minimize the first two improper uses.
Manufacturers have also attempted to minimize the second improper use by including a dead-man switch with their heating pads. A dead-man switch is a lever or button that must be continuously depressed to maintain operation of the pad. Should the user fall asleep during use, the user will release the dead-man switch shutting off the heating pad. However, some users have been known to circumvent the dead-man switch by tying down the dead-man switch thereby overriding the safety aspect of the dead-man switch. Other manufacturers have eliminated the dangers of users tying down dead-man switches with an on/off switch with a maximum heating time of 20 minutes. The on switch allows the user to restart the 20-minute timer any time by pushing the on button or end the session by pushing the off button. If the user falls asleep or forgets to press the off button, the built-in-timer will automatically shut the unit off for safety. However, neither the dead-man switch nor the on/off switch with an automatic timer address the first misuse identified above.
Accordingly, there is a need for an improved electric heating pad that eliminates exposure to extreme temperatures when both faces of the heating pad are covered.